Effect of strain rate and temperature on strain hardening behavior of a dissimilar joint between Ti–6Al–4V and Ti17 alloys
Effect of strain rate and temperature on strain hardening behavior of a dissimilar joint between Ti–6Al–4V and Ti17 alloys
复制标题
DOI：
10.1016/j.matdes.2013.11.003
复制
发表时间：
2014-04
影响因子：
8.4
通讯作者：
S. Q. Wang;Junting Liu;D. Chen
中科院分区：
文献类型：
--
作者：
S. Q. Wang;Junting Liu;D. Chen
研究了应变速率和温度对Ti-6Al-4V和Ti-17（Ti-5Al-4 Mo-4Cr-2Sn-2 Zr）钛合金电子束焊接接头拉伸性能、应变硬化行为、应变速率敏感性和断裂特性的影响。焊接导致整个接头的显微组织发生显著变化，在熔合区（FZ）中为六方密排马氏体（α′）和正交马氏体（α″），在Ti-6Al-4V侧的热影响区（HAZ）中为α′，而在Ti-17侧的HAZ中为粗大β。在异种接头上观察到明显的不对称硬度分布，FZ中的硬度最高，Ti-6Al-4V侧的硬度低于Ti 17侧，其中存在软区。尽管塑性略有下降，接头的屈服强度（YS）和极限拉伸强度（UTS）位于Ti-6Al-4V和Ti-17两种母材（BM）之间，Ti-17合金具有更高的强度。随着应变速率的增加或温度的降低，接头的屈服强度、抗拉强度和Voce应力均增大，而硬化能力和应变硬化指数均减小。屈服后，接头中发生了第三阶段硬化。硬化速率强烈依赖于应变速率和温度。在给定的真应力下，随着应变速率的增加或温度的降低，应变硬化率增加。应变率敏感性通过共同的方法和Lindholm方法进行评估，观察到随着真实应变的增加而降低。Ti-6Al-4V BM焊接接头在热影响区附近基本失效，断口在不同温度下均呈现韧窝断裂特征。
The aim of this study was to evaluate the influence of strain rate and temperature on the tensile properties, strain hardening behavior, strain rate sensitivity, and fracture characteristics of electron beam welded (EBWed) dissimilar joints between Ti–6Al–4V and Ti17 (Ti–5Al–4Mo–4Cr–2Sn–2Zr) titanium alloys. The welding led to significant microstructural changes across the joint, with hexagonal close-packed martensite (α′) and orthorhombic martensite (α″) in the fusion zone (FZ),α′ in the heat-affected zone (HAZ) on the Ti–6Al–4V side, and coarseβin the HAZ on the Ti17 side. A distinctive asymmetrical hardness profile across the dissimilar joint was observed with the highest hardness in the FZ and a lower hardness on the Ti–6Al–4V side than on the Ti17 side, where a soft zone was present. Despite a slight reduction in ductility, the yield strength (YS) and ultimate tensile strength (UTS) of the joints lay in-between the two base metals (BMs) of Ti–6Al–4V and Ti17, with the Ti17 alloy having a higher strength. While the YS, UTS, and Voce stress of the joints increased, both hardening capacity and strain hardening exponent decreased with increasing strain rate or decreasing temperature. Stage III hardening occurred in the joints after yielding. The hardening rate was strongly dependent on the strain rate and temperature. As the strain rate increased or temperature decreased, the strain hardening rate increased at a given true stress. The strain rate sensitivity evaluated via both common approach and Lindholm approach was observed to decrease with increasing true strain. The welded joints basically failed in the Ti–6Al–4V BM near the HAZ, and the fracture surfaces exhibited dimple fracture characteristics at different temperatures.